The invention relates to a method for applying cement under pressure to bone cavities or interstices, for example for treating osteoporosis and for repairing bone prosthesis in situ, particularly artificial hip joints,
A conventional technique for treating hip diseased hip joints involves the replacement of the patients diseased hip joint by the substitution of a prosthetic hip joint having a pin which is anchored by cement in the femur cavity to secure the hip joint to the femur. When fitting the joint, the top of the femur in the region of the trabeculae is cut open and the bone marrow removed through the top opening by a scooping and suction technique, emptying the bone cavity or intra/medullary canal for the receipt of the pin and a two-part epoxy cement injected into the cavity through the top opening to spread around the pin using a gun, similar in construction to a caulking gun. Caps of various selected sizes are required to be fitted around the gun nozzle to seal the top opening during injection in an attempt to permit a relatively modest pressure increase to perhaps 2-3 p.s.i. in an attempt to completely fill all interstices around the pin.
However, the pin is made of titanium which is much harder than the cement and as a result of the difference in hardness, after the joint has been in use for a number of years, typically about 10 years, hairline cracks or interstices develop at the interface of the titanium pin and epoxy cement. The conventional remedy has required that the entire joint (pin) be removed and replaced which is effectively a repeat of the earlier procedure which is an undesirable major operation.
It is also known to completely fill a medullary canal with cement through an opening cut in the bone in the upper end for the treatment of osteoporosis.
Examples of devices and mechanisms previously used to instal the artificial joint are described in the catalogue of Stryker Instruments, Ml, PT No 1000-119 rev C; PT. NO. 1000-310 REV B1; BP NO 1000-340 for their bone preparation systems, third generation cementing technique and cement injection system.
It is one object of the invention to provide a method which will obviate the requirement to remove and replace the artificial joint as a result of the development of hairline cracks or interstices at the interface of the prosthesis pin and cement.
It is another object of the invention to provide a method permitting the injection of the cement at very high pressures into the bone cavity or medullary canal and interstices to ensure maximum intrusion of cement therein.
According to one aspect, the invention provides a method for repairing a join between a prosthetic anchoring pin and a bone receiving the pin, without removing the pin from the bone including the steps of:
tapping entry and exit bores at spaced apart locations in the bone in communication with opposite ends of an interstice formed at a interface of the pin;
providing a pair of adaptors and a zerk, each adaptor comprising an elongate body with leading, penetrating and rear, connecting ends, the body having a pointed penetrating shank which tapers outward as it extends rearward from the leading end and is formed with an external self-tapping screw thread and a fingerpiece comprising a pair of wings protruding radially outward adjacent the rear end and an internal cement passageway extending axially completely through the body communicating with leading and rear ends, the rear end of at least one adaptor being provided with an internal screw thread meshing with a complementary thread on the zerk and manually screwing the adaptors into sealing engagement with respective bores;
providing a high pressure cement gun and attaching the zerk to the cement outlet of the cement gun and to the rear end of said at least one adaptor;
providing an outlet hose for the cement gun and securing the outlet hose to the zerk
and injecting cement under high pressure from the gun through said at least one adaptor to penetrate throughout the interstice traveling from the entry hole to the exit hole thereby filling the interstice to seal and repairing the join.
The invention enables repair of a hairline crack or interstice in a join between a prosthetic anchoring pin and a anchoring cement in bone receiving the pin, without removing the pin from the bone.
According to another aspect, the invention provides A method for treating osteoporosis comprising the steps of:
tapping entry and exit bores at spaced apart locations in an affected bone in communication with opposite ends of a medullary canal of the bone:
providing a pair of adaptors and a zerk, each adaptor comprising an elongate body with leading, penetrating and rear, connecting ends, the body having a pointed penetrating shank which tapers outward as it extends rearward from the leading end and is formed with an external self-tapping screw thread and a fingerpiece comprising a pair of wings protruding radially outward adjacent the rear end and an internal cement passageway extending axially completely through the body communicating with leading and rear ends, the rear end of at least one adaptor being provided with an internal screw thread meshing with a complementary thread on the zerk and, manually screwing the adaptors into sealing engagement with respective bores;
providing a high pressure cement gun and attaching the zerk to the cement outlet of the cement gun and to the rear end of said at least one adaptor;
providing an outlet hose for the cement gun and securing the outlet hose to the zerk,
and injecting cement under high pressure from the gun through said at least one adaptor into said medullary canal to penetrate throughout the canal traveling from the entry hole to the exit hole thereby filling the canal and reinforcing the bone.
The screw threaded adaptor and zerk seal against back pressure enabling a lever operated, hydraulic action, gun known for greasing automobiles and which is widely available at low cost to be used for regluing operations to apply glue rapidly under very high pressure (e.g. 7,500 psi-10,500 p.s.i.). Furthermore, as the adapters have fingerpieces they may, with zerks attached, readily be screwed by hand into pilot bores tapped in the boney mass
Aspects of various devices described herein are described in my application Ser. No: 09/346861, filed: Jul. 2, 1999, the disclosure of which is incorporated herein by reference.